Automatic License Plate Reading (ALPR) systems are used by security and law enforcement personnel to find and read vehicle license plate numbers in images produced by video cameras and still cameras. A typical ALPR system consists of a video imaging device, a video capture device and a computer running ALPR software. The video camera sends video images to the video capture device as a standard television format video signal. The video capture device converts the video signal into digital image information and stores the digital information in the computer. The computer's software then begins the ALPR process by locating the license plate in the image as represented by the digital information. If a license plate is detected in the image, the computer software performs a character recognition process to “read” the license plate number.
State governments typically issue vehicle license plates having alphanumeric characters combined with decorative design elements having various colors. The arrangement of information and design elements on the plates, including color characteristics, may be helpful in identifying the state that issued a plate. However, variations in design from state-to-state make it more difficult for ALPR systems to recognize and process the license plate number.
What is needed is a method for processing character and design information on a vehicle license plate to aid in identifying the state of issuance of the plate, and for using the state identification information in processing the license plate number.